Question: On the first 3 tests of his physics class, Omar got an average score of 82. What does he need on the next test to have an overall average of 86?
Let his score on the next test be $x$ The sum of all of his scores is then $3 \cdot 82 + x$ The same sum must also be equal to $4 \cdot 86$ Solve: $x = 4 \cdot 86 - 3 \cdot 82 = 98$.